#carres{
    position: relative;
    width: 1500px;
    height: 1500px;
}

#carres div{
    position: absolute;
    width: 300px;
    height: 300px;
    opacity: 0.5 ;
}


#carre1 {
    background: red ;
    top: 400px;
    left: 500px;
}
#carre2 {
    background: blue ;
    top: 400px;
    left: 100px;
}
#carre3 {
    background: green;
    top: 200px;
    left: 300px;
}
#carre4 {
    background: yellow ;
    top: 250px;
    left: 700px;
}
#carre5 {
    background: violet;
    top: 50px;
    left: 200px;
}